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Original question:

UCC28070：ucc28070 1200W PFC 電源 切換開關尖波

UCC28070A: Component design

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Prodigy 90 points
Part Number: UCC28070A

Tool/software:

Hi team, 

this is my schematic design  .

I want to do a boost PFC circuit(non-interleaved), the input line frequency is 50~10000Hz ,input Voltage :15~50Vac, Output voltage:90V, output power:100W,switching frequency is 300kHz.

I design my inductance is 70uH.

When I test the circuit, PWM is so weird. and it is not PFC .

The waveform below

The input line frequency is 60Hz, input voltage is 30Vac.

I wanna know whether  my components design is wrong? And how to fix it

  • 0
    TI__Mastermind 32450 points

    Hello, 

    Much of your problem very likely comes from the set-up of your current-sense transformer (CT) circuit for CSA. 
    You have a 10k resistor as the burden resistance after the CT diode.  That makes the CSA signal very large for even a small amount of inductor current.  

    That 10kR belongs on the anode-side of the CT diode, and a much lower value (probably something < 100R) goes where the 10k is shown now. 
    Please fill out this calculator tool (https://www.ti.com/tool/download/SLUC114 ) to determine the recommended value for the CT burden resistor and then divide that value in half.
    This is because the tool expects to design for interleaved phases.  With only one phase active, there will be twice as much current in that phase than what the tool is calculating with. 

    It should help you determine other values as well, although I'm not sure it can accurately accommodate your low input voltage range.  (The tool is optimized for the usual 85Vrms ~ 265Vrms input range.)

    The UCC28070A will not function correctly for input line frequency higher than 800Hz.  10kHz line frequency is far beyond the capability of this IC to deal with.  
    Even 800Hz may have higher THDi than with lower AC frequencies. 
    I recommend to keep your evaluations to 50Hz to 400Hz input range. 

    Regards,
    Ulrich